In oil and gas exploration and development operations it may be desirable to remove casing that has previously been set in the wellbore. In the drilling of oil and gas wells, concentric casing strings are installed and cemented in the borehole as drilling progresses to increasing depths. Each new casing string is supported within the previously installed casing string, thereby limiting the annular area available for the cementing operation. Casing removal involves severing a section of the casing string and pulling the free end to the surface to remove the severed section. Typically, a downhole tool having cutters thereon may be run into the casing multiple times to cut and extract sections of casing until complete. For instance, a cutting device may first be lowered into the wellbore to cut the casing at a desired depth, after which the cutting device is returned to the surface. Subsequently, a spearing device may then be lowered downhole to engage a free end of the severed casing. Once the free end of the casing is engaged the section of severed casing may be pulled from the wellbore.
In certain situations, difficulties may arise in which the severed casing is unable to be pulled from the wellbore, for example, the casing was not severed adequately at a certain location. In this case, the spearing device is removed, the cutting device reinserted in the wellbore, and a second cut may be made in the casing string at a second location in another attempt to sever the section of casing. Attempts to remove the casing with the spearing device may again be commenced and this process repeated until the section of casing is successfully severed and removed. Depending on the number of cuts required to sever the casing, multiple trips into the wellbore may be required before the casing is severed and removed. Thus, overall time and costs involved in completing a casing extraction may be greatly increased.
Accordingly, there exists a need for apparatus and methods capable of reducing the number of trips required into the wellbore to sever and remove casing.